Electroencephalography (EEG) signal complexity reflects the richness of brain activity and is considered a marker of consciousness. However, its normative values across physiological conscious states using intracranial EEG (iEEG) across cortical areas remain poorly defined. We aimed at referencing iEEG complexity in the human brain and its links with global states of consciousness. We analyzed 5,703 iEEG recordings from healthy cortices in 106 participants during wakefulness, N2, N3, and REM sleep, using complementary markers: Kolmogorov complexity, permutation entropy, and spectral entropy. An independent dataset comprising 474 recordings was used for validation and added data on epileptic cortices and propofol anesthesia. iEEG complexity decreased with reduced consciousness, with the highest values in wake/REM and the lowest under propofol. Complexity was more variable during N2/N3 sleep. Frontoparietal regions exhibited the highest complexity in conscious states. Epileptic cortex showed lower complexity than healthy cortex during wake and REM. A random forest classifier reliably classified sleep stages using complexity markers. Markers of iEEG signal complexity reliably index global states of consciousness. These normative data support the use of complexity as a marker of physiological consciousness, cortical integrity, and sleep-stage detection.

Speech production requires the rapid coordination of a complex hierarchy of linguistic units, transforming a semantic representation into a precise sequence of articulatory movements. To unravel the neural mechanisms underlying this feat, we leverage recordings from eight 3.2 x 3.2 mm 64-microelectrode arrays implanted in the motor cortex and inferior frontal gyrus of two patients tasked to produce twenty thousand sentences. We show that a hierarchy of linguistic features are robustly encoded in most of these small cortical patches. Contrary to our expectations, instead of a clear macroscopic organization between patches, we observe a multiplexing of phonetic, syllabic and lexical representations within each cortical patch. Critically, this coding scheme dynamically changes over time to allow successive phonemes, syllables and words to be simultaneously represented without interference. Overall, these results, reminiscent of position encoding in transformers, show how small cortical patches organize the unfolding of the speech hierarchy during language production.

Restoring communication for people who have lost the ability to speak or move after a brain injury is a major challenge. While intracranial implants now enable high-performing brain-computer-interfaces, non-invasive alternatives are still lagging behind. Here, we present Brain2Qwerty v2, a model that can decode the production of natural sentences solely from real-time magnetoencephalography (MEG) recordings. By collecting 22,000 sentences typed by nine subjects, each recorded for 10 hours, our model leverages character, word and sentence-level representations to achieve an average word error rate (WER) of 39

Decoding speech from brain activity has typically relied on limited neural recordings collected during short and highly controlled experiments. Here, we introduce a framework to leverage week-long intracranial and audio recordings from patients undergoing clinical monitoring, effectively increasing the training dataset size by over two orders of magnitude. With this pretraining, our contrastive learning model substantially outperforms models trained solely on classic experimental data, with gains that scale log-linearly with dataset size. Analysis of the learned representations reveals that, while brain activity represents speech features, its global structure largely drifts across days, highlighting the need for models that explicitly account for cross-day variability. Overall, our approach opens a scalable path toward decoding and modeling brain representations in both real-life and controlled task settings.

INTRODUCTION:Idiopathic intracranial hypertension (IIH) is severe condition affecting patients' vision and quality of life. When medical treatment is insufficient, an invasive approach may be proposed, consisting of either performing a ventricular shunt or stenting a stenosed venous sinus. The aim of this study is to compare these two techniques. METHODS:All patients who received one of these treatments for IIH associated with papilledema over a 5-year period were analysed. The primary outcome was the resolution of papilledema at 3 months coupled with the absence of complications. RESULTS:Over a 5-year period, 101 patients were analysed, of whom 61 underwent endovascular treatment and 40 underwent surgical treatment. Resolution of papilledema at three months without complications was achieved in 72% of cases in the surgical group and in 89% of cases in the endovascular group (p = 0.04). There was a higher proportion of IIH in the surgical group (60% vs 1.6%, p < 0.001) associated with higher intracranial pressure (38.8 vs 33.1 cmH2O) and more severe visual impairment (55% vs 15%). Resolution of papilledema at three months, headache, tinnitus, and visual improvement did not differ significantly between the groups. The average time to improvement was significantly (p < 0.0001) shorter in the surgery-treated group (3.62 vs 8.74 weeks). CONCLUSION:Endovascular treatment appears to have a better benefit-risk balance compared to surgery, with the caveat that the surgery group had a more severe presentation in this study. This encourages the conduction of a randomized study to have two homogeneous groups.

A few million words suffice for children to acquire language. Yet, the brain mechanisms underlying this unique ability remain poorly understood. To address this issue, we investigate neural activity recorded from over 7,400 electrodes implanted in the brains of 46 children, teenagers, and adults for epilepsy monitoring, as they listened to an audiobook version of "The Little Prince". We then train neural encoding and decoding models using representations, derived either from linguistic theory or from large language models, to map the location, dynamics and development of the language hierarchy in the brain. We find that a broad range of linguistic features is robustly represented across the cortex, even in 2-5-year-olds. Crucially, these representations evolve with age: while fast phonetic features are already present in the superior temporal gyrus of the youngest individuals, slower word-level representations only emerge in the associative cortices of older individuals. Remarkably, this neuro-developmental trajectory is spontaneously captured by large language models: with training, these AI models learned representations that can only be identified in the adult human brain. Together, these findings reveal the maturation of language representations in the developing brain and show that modern AI systems provide a promising tool to model the neural bases of language acquisition.

Humans effortlessly communicate their thoughts through intricate sequences of motor actions. Yet, the neural processes that coordinate language production remain largely unknown, in part because speech artifacts limit the use of neuroimaging. To elucidate the unfolding of language production in the brain, we investigate with magnetoencephalography (MEG) and electroencephalography (EEG) the neurophysiological activity of 35 skilled typists, while they typed sentences on a keyboard. This approach confirms the hierarchical predictions of linguistic theories: the neural activity preceding the production of each word is marked by the sequential rise and fall of context-, word-, syllable-, and letter-level representations. Remarkably, each of these neural representations is maintained over long time periods within each level of the language hierarchy. This phenomenon results in a superposition of successive representations that is supported by a hierarchy of dynamic neural codes. Overall, these findings provide a precise computational breakdown of the neural dynamics that coordinate the production of language in the human brain.

Despite decades of research, we still do not understand how spontaneous human seizures start and spread – especially at the level of neuronal microcircuits. In this study, we used laminar arrays of micro-electrodes to simultaneously record the local field potentials and multi-unit neural activities across the six layers of the neocortex during focal seizures in humans. We found that, within the ictal onset zone, the discharges generated during a seizure consisted of current sinks and sources only within the infra-granular and granular layers. Outside of the seizure onset zone, ictal discharges reflected current flow in the supra-granular layers. Interestingly, these patterns of current flow evolved during the course of the seizure – especially outside the seizure onset zone where superficial sinks and sources extended into the deeper layers. Based on these observations, a framework describing cortical-cortical dynamics of seizures is proposed with implications for seizure localization, surgical targeting, and neuromodulation techniques to block the generation and propagation of seizures.

Recent advances in material technology and in micro- and nano-electronics have profoundly changed the design of intracranial electrophysiology electrodes. It is now possible to manufacture electrodes that record cortical activity at a spatial resolution that was previously unthinkable. This high spatial resolution enables recording of the functional structures of the brain, and differentiation of the activity of the different types of neurons composing them. In this paper, we present a review of the different types of electrodes now available, and then suggest one of the first applications for such high resolution electrodes, namely a means to better characterise the mechanisms that generate focal seizures in epileptics. Finally, we reflect more broadly on prospects for their future use.

Within the neurosurgeon's armamentarium, stereoelectroencephalography (SEEG)-guided radiofrequency thermocoagulation (RFTC) is an elegant tool to manage epilepsy in selected cases. This technique can 1) be curative when targeting small-volume ictal onset zones, 2) be used as a diagnostic tool by observing the consequences of coagulation on seizures or by recording the epileptic network in SEEG, and 3) offer palliative treatment through multiple lesions within a wide epileptic network. It is performed on awake patients, under continuous neurological evaluation, while monitoring impedance, time, and energy delivered. It could offer highly favorable outcomes in some cases, as in periventricular nodular heterotopia where 81% of patients are responders.

To explore amide proton transfer-weighted imaging (APTwi) for the initial classification of brain masses in clinical practice by systematically reporting APTwi signal intensity (APT-SI) in tumor mimics and brain tumors. Single-center retrospective analysis (2017–2020) of APTwi in 156 patients (84 men, mean age: 50.9 ± 20) who underwent characterization imaging of a brain mass prior to any treatment, using 3-Tesla MRI. 125/156 (80

ObjectivesSpontaneous intracranial hypotension (SIH) is frequently complicated by subacute subdural hematoma (SDH) and more rarely by bilateral thalamic ischemia. Here, we report a case of SIH-related SDH treated with three epidural patches (EPs), with follow-up of the intracranial pressure and lumbar intrathecal pressure.MethodsA 46-year-old man presented bilateral thalamic ischemia, then a growing SDH. After failure of urgent surgical evacuation, he underwent three saline EPs, two dynamic myelography examinations and one digital subtraction angiography–phlebography examination. However, because of no dural tear and no obstacle to the venous drainage of the vein of Galen, no therapeutic procedure was available, and the patient died.ResultsThe case exhibited a progressive increase in the transmission of lumbar intrathecal pressure to intracranial pressure during the three EPs. The EPs may have successfully treated the SIH, but the patient did not recover consciousness because of irreversible damage to both thalami.ConclusionClinicians should be aware of the bilateral thalamic ischemia picture that may be the presenting sign of SIH. Moreover, the key problem in the pathophysiology of SIH seems to be intraspinal and intracranial volumes rather than pressures. Therefore, intracranial hypotension syndrome might actually be an intraspinal hypovolume syndrome.

The bidirectional transmission between cortical and subcortical regions is facilitated by the thalamus and this crucial role makes the thalamus a target for controlling many disorders. While thalamic neuromodulation has been shown to reduce seizure frequency by more than 50% in some patients with epilepsy, its efficacy is highly variable across patients. In this study, we aim to understand thalamic involvement in seizures and whether such seizures share a specific feature. Seizures (n=36) recorded from five patients who received thalamic implants as part of their presurgical evaluation were analyzed. For each seizure, the seizure onset times/zones were visually identified. The coherence between seizure onset zones and the ipsilateral thalamic nuclei (SOZ-IT), as well as that between the left and right thalamus (LT-RT), was measured for different frequency bands (delta, theta, alpha, beta, gamma). The coherence for each frequency band then was averaged over seizures for each patient/seizure onset. For each seizure type, the SOZ-IT coherence was compared to the coherence of the rest of the contacts with the thalamus for each frequency band. We found that alpha coherence is most correlated with seizure onset, always increasing at seizure onset between SOZ-IT in all focal seizures. Surprisingly, in seizures with generalized onset, the increased coherence was prominent in the alpha frequency band, but it was highest between LT-RT at seizure onset rather than between the cortex and thalamus. These initial findings suggest that the thalamus could mediate seizure-related activity and facilitate seizure propagation in focal and generalized seizures. However, the dynamics of this facilitation differ for generalized and focal seizures. In focal seizures, seizure propagation may be facilitated by LT-RT interactions, which are more involved in generalized seizure generation. We anticipate that an improved understanding of the extent of thalamic involvement will improve our ability to manage different seizures. Research Category and Technology and Methods Translational Research: 21. Neurophysiology Keywords: Epilepsy, Seizure, Thalamus, Coherence

Primary hemifacial spasm (pHFS) is a benign but disabling movement disorder caused by a neurovascular conflict involving the facial nerve. Surgical treatment by microvascular decompression (MVD) is the most effective therapeutic. Predictors of surgical failure and surgical complications are still lacking. The aim of this study is to identify such predictors through the retrospective analysis of a series of 200 consecutive patients. All patients who underwent MVD for pHFS from January 1991 to December 2017 were included. All patients had at least two years follow-up. In addition to the demographic data, the outcome and the complications were collected. The primary outcome analysis showed that 7.5% of patients had a recurrence. Multiple and AICA related neurovascular conflicts were statistically associated to a higher recurrence rate after MVD (respectively p < 0.001 and p = 0.02). Permanent facial palsy occurred in 2.5% of patients, hearing loss in 9.0% (2.0% of complete unilateral impairment) and dizziness in 2.5%. The risk of each of these peripheral neurological impairments was statistically increased by a long duration between the first pHFS symptom and the MVD (p < 0.001). In case of recurrence, a second MDV was offered. Long term follow-up showed that all patients had a complete resolution of the HFS. Post-operative complication rate was not significantly increased after a second MVD. Multiple and AICA related neurovascular conflicts are associated to a higher risk of surgical failure. When a pHFS recurrence occurs, a second surgical procedure is associated with excellent outcome without significant increase of post-operative complications and should therefore be recommended.

Objectives:Convexity spontaneous subacute subdural hematoma (CSSSH) frequently relapse after one or more surgical drainages. This may be due to spontaneous intracranial hypotension (SIH), for which the gold standard treatment is the epidural blood patch. In this study, we report 4 cases of refractory CSSSH treated with rescue epidural saline patch, although history and imaging studies showed no evidence of SIH.Methods:All 4 patients received a lumbar saline epidural rescue patch for consciousness impairment associated with refractory CSSSH, and one is particularly detailed. No patient had typical radiologic signs of SIH or, on the contrary, uncal herniation that could have indicated intracranial hypertension.Results:The Glasgow Coma Scale score improved significantly in the days after application of the epidural patch in 3 patients. All patients showed an improvement of the CT scan. Two patients underwent lumbar pressure measurement to confirm low values before the epidural injection, and for one, the intrathecal pressure profile during epidural patching is presented.Discussion:An epidural patch may be considered in managing CSSSH with no uncal herniation, even in the absence of signs of SIH on brain and spinal imaging. Whether it should be combined with surgical evacuation or used as first-line therapy remains to be determined.

Objectifs pédagogiques : – présenter les signes IRM évoquant une hypertension intracrânienne idiopathique ; – implémenter un protocole adéquat pour les rechercher ; – rechercher les principaux diagnostics différentiels.

OBJECTIVE Percutaneous balloon compression (PBC) is a popular treatment option for trigeminal neuralgia. However, the efficacy of PBC is widely considered to be associated with the occurrence of sensitive complications, although neither this correlation nor the underlying mechanisms have been established. The objectives of the present study were to identify factors predicting time to pain recurrence after PBC and identify factors predicting a severe sensitive complication. METHODS The authors conducted a retrospective study on patients who underwent PBC for the first time between 1985 and 2019 in two French hospitals. Data were retrieved from patients’ medical records. Potential clinical and radiological predictors for time to pain recurrence and severe sensitive complication were evaluated using a Cox model and a logistic regression, respectively. RESULTS A total of 131 patients were included in the study, with a median follow-up of 3.0 years. Pain recurrence occurred in 77 patients, and the median time to pain recurrence was 2.0 years. In the multivariate analysis, six independent factors predicting pain recurrence were identified: 1) longer duration of presurgical symptoms; 2) localization of the pain along the mandibular branch of the trigeminal nerve (V3); 3) atypical pain; 4) diagnosis of multiple sclerosis; 5) use of a medical device not specifically adapted for trigeminal neuralgia surgery; and 6) duration of balloon compression > 60 seconds. Regarding the secondary objective, 26 patients presented a severe sensitive complication after PBC, which the authors defined as the development of a new sensitivity disorder of the cornea, deafferentation pain known as anesthesia dolorosa, and/or long-lasting hypoesthesia augmentation characterized by the new appearance or increase in size or intensity of an area of hypoesthesia in the face for at least 3 months. The only predictor associated with a severe sensitive complication in the multivariate analysis was compression duration > 60 seconds. CONCLUSIONS These results show that the risk of postoperative complications can be assessed at the patient level, the most important modifiable parameter being the time of compression by the balloon. Although this study shows the relevance of a personalized medicine approach, its clinical application remains to be validated.

Secondary to the creation of a surgical corridor and retraction, white matter tracts degenerate, causing long-term scarring with potential neurological consequences. Third and lateral ventricle tumors require surgery that may lead to cognitive impairment. Our objective is to compare the long-term consequences of a transcortical transfrontal approach and an interhemispheric transcallosal approach on corpus callosum and frontal white matter tracts degeneration. Surgical patients with ventricular tumor accessible through both approaches were included and clinico-radiological data were retrospectively analyzed. The primary endpoint was the callosotomy length at 3-month post-operative T1 MRI, corrected by the extension of the tumor and the use of neuronavigation. Secondary outcomes included perioperative criteria such as bleeding, use of retractors and duration, FLAIR hypersignal on 3-month MRI, and re-do surgeries. To assess white matter tract interruption, 3-month FLAIR hypersignal was superposed to a tractography atlas. Seventy patients were included, 57 (81%) in the transfrontal group and 13 (19%) in the interhemispheric group. There was no difference in the mean callosotomy length on 3-month MRI (12.3 mm ± 5.60 transfrontal vs 11.7 mm ± 3.92 interhemispheric, p = 0.79) on univariate and multivariate analyses. The callosotomy length was inferior by − 3.13 mm for tumors located exclusively in the third ventricle (p = 0.016), independent of the approach. Retractors were used more often in transfrontal approaches (60% vs 33%, p < 0.001). The extent of frontal FLAIR hypersignal was higher after transfrontal approach (14.1 mm vs 0.525 mm, p < 0.001), correlated to the use of retractors (p < 0.05). After the interhemispheric approach, no tract other than corpus callosum was interrupted, whereas, after the transfrontal approach, frontal arcuate fibers and projections from the thalamus were interrupted in all patients, the cingulum in 19 (33%), the superior fronto-occipital fasciculus in 15 (26%), and the superior longitudinal fasciculus in 2 (3%). Transfrontal and interhemispheric approaches to the third and lateral ventricles both lead to the same long-term damage to the corpus callosum, but the transfrontal approach interrupts several white matter tracts essential to cognitive tasks such as attention and planning, even in the non-dominant hemisphere. These results encourage all neurosurgeons to be familiar with both approaches and favor the interhemispheric approach when both can give access to the tumor with a comparable risk. Neuropsychological studies are necessary to correlate these anatomical findings to cognitive outcomes.

(Stable 3) Comparison of the statistical values of the multiple regression analyses (which used the mean values of signi fi cant clusters of fALFF, and brain activity as dependent variables) obtained with and without the use of rGMD and rCSFD as covariates, (Stable 4) Psychometric scale scores in each genotype of males and females based on the number of the risk allele of the ITIH3 rs2535629 polymorphism.